Typical fifth wheel devices known in the industry are illustrated in prior U.S. Pat. Nos. 2,861,818 to Kayler et al and 4,871,182 to Altherr et al, the disclosures of which are incorporated herein by reference. Such fifth wheel devices include a plate which supports the forward bed plates of a trailer. A king pin is fixed to the trailer bed plate and extends into a center opening of the fifth wheel plate. Fifth wheels have included a pivotally mounted jaw under the plate to engage and hold a king pin against horizontal withdrawal. Normally, the jaw automatically closes and is engaged by a spring loaded bolt or bar to become locked on the king pin as the tractor and trailer are brought together. However, there is typically also a mechanism provided to extract and hold the locking bolt so as to unlock the jaw and permit horizontal release of the king pin to allow separation of tractor and trailer when the trailer is stationary and the tractor is powered forward. That mechanism is normally operable manually by a driver or assistant and usually includes safeguards so as to avoid accidental king pin release. The driver or assistant must dismount the truck, unlock the jaw and then remount the tractor before it is powered forward.
In the prior designs, illustrated in the aforementioned patents, that mechanism to extract and hold the locking bolt has included an operating rod that had to be both pulled linearly away from the fifth wheel and simultaneously lifted or twisted so as to latch and hold the bolt against premature return to reengage the pivotable jaw before the driver separated the tractor and trailer. Such lifting and twisting motions are difficult to perform particularly for small stature drivers, and require a relatively large space between tractor frame and trailer bed for manipulation of the operating rod.
Thus it would be advantageous if the lifting and twisting motion required for a fifth wheel operating rod could be eliminated and if the locking bolt could be modified so as to self latch and unlatch for properly sequenced engagement with the fifth wheel jaw.